IBM's 35 atoms and the rise of nanotech

...for this general idea, called spintronics, uses spin to control the flow of electric current, but Eigler wants to use spin alone.

"My goal is to do everything we need to do for computation — logic, storage, information transport — but without moving electrons around at all," Eigler said.

One advantage of the approach is that it avoids electrical current that produces the waste heat that is a major limiting factor in today's computers. Another is that it can enable three-dimensional computing designs much more densely packed with processing power than today's two-dimensional circuitry etched onto silicon wafers.

Spin engineering
The spin of one atom can affect that of its neighbour. The hard part is arranging atoms in order to harness that effect and perform useful computing operations.

"We have to learn how to engineer things so they work the way we want them to work. If you have two atoms, each has spin, and those spins are coupled together in usually two, three, or even four different ways," he said. "You have to place them in the appropriate relationship with one another."

One milestone towards this goal was work by Gerhard Meyer of IBM's Zurich Research Laboratory and others to store data in the form of electrical charges on individual atoms of gold, Eigler said.

In another, IBM's Christopher Lutz found he could trigger a 'molecule cascade', in which a series of carbon monoxide molecules could transmit information. The metastable molecules could store energy, then release it from one neighbour to another, similar to a chain of balanced dominoes falling.

Lutz then found a way to arrange those molecules into basic logical processing units of computers, 'and gates' and 'or gates', which are foundations of today's computers. It did not use spin, but it is a step in that direction, Eigler said.

Building blocks
One possible intermediate step between moving single atoms and mass manufacturing is what Eigler calls nano plug-ins.

If physicists and engineers could figure out how to construct individual logic gates out of a complicated molecule, IBM chemists might be able to work out a way to synthesise such units in quantity. Next would come the assembly process of snapping these units together appropriately.

"That strategy for building things that work on a very small scale may well be what we see in the future," Eigler said.

And it may arrive, even if his spin-based computation does not. "It may be [used with] regular conventional electronics, [or] with carbon nanotubes or graphene," he said. This brings him to the point about why IBM Research invests in such distantly useful technologies.

"The knowledge we're generating in the process of getting there," Eigler said, "is likely to feed into the industry much sooner than the actual outcome — if we ever get to that outcome".